CCR First Stage Regs - IP Stability

[tbone1004]

the transmitter is required to maintain direct contact with ambient pressure. The difference in area between the two sides of the transmitter equate to the "thumbtack principal"
If the two sides are equal in area, then there will be a 1:1 transmission of pressure. If the side facing the ambient pressure is larger than the side inside of the regulator, there will be an increase in pressure transmitted, this is what goes in in the Apeks first stage. The area of the black plastic transmitter is larger than the area of the metal spring holder that it presses against.
If the carrier is larger, then the pressure being transmitted will be reduced.
All basic physics.

 

[cathal]

Just my 2C, but if you check back on the posts you got those diagrams from, I believe the cause of the drop in I.P at the highest pressure was that the plastic Hydrostatic Transmitter became deformed under these high pressures. They actually had accompanying photos of the remains of the transmitters. So what would happen to these regs at these extreme depths were that you would get less and less gas out of them.
From what we can see it happened to both regs in your diagrams but at a much later stage for the scubapro. This would lead me to believe that the scubapro Hydrostatic Transmitter is made with a material that has a much greater resistance to crushing/I.P than the Apeks plastic one, hence the delivery of a more stable I.P.

Best I can do is a video of this failure occurring in a pressure pot:
And an accompanying paper: http://eng.rb-forum.cz/data/uploads...Y7p2cYtDVNDwYHGWtEsc3MDuaetFSaYNtsXCdnl1Z-RIM

 

[runsongas]

you can take the transmitter out and fill it with lube atomic/sp spec style

 

[rsingler]

you can take the transmitter out and fill it with lube atomic/sp spec style

That's a great suggestion!
How many environmentally sealed regs do you come across, where the seal is "domed" because it's lost its seal at some time in the past, and has an air bubble underneath? That bubble is a compressible space that reduces the response of the reg at depth until the bubble is heavily compressed. Filling with lube would obviate that completely!
Great suggestion!

The Apeks has a plastic bit under the sealing rubber that pushes on the diaphram when external pressure is applies (more depth = more pressure). I know of many people that have removed that bit to keep the IP stable.

Is that what you meant in this comment, @Dsix36 ?
If so, I apologize for the tone of my response.

 

[tbone1004]

you can take the transmitter out and fill it with lube atomic/sp spec style

yeah don't do that, your repair tech will hate you and it's pointless. If you're going to fill it with something, since it is normally air sealed, I'd fill it with alcohol a la Poseidon used to

 

[rsingler]

I'd fill it with alcohol a la Poseidon used to

That works for me!

 

[Dsix36]

That's a great suggestion!
How many environmentally sealed regs do you come across, where the seal is "domed" because it's lost its seal at some time in the past, and has an air bubble underneath? That bubble is a compressible space that reduces the response of the reg at depth until the bubble is heavily compressed. Filling with lube would obviate that completely!
Great suggestion!


Is that what you meant in this comment, @Dsix36 ?
If so, I apologize for the tone of my response.

Nope. The ones I have know about either removed it completely or shaved a bit off the end to reduce the length. I never felt comfortable with the idea of screwing with it. I just turned down my IP for deep stuff, with helium, so the ADV would not leak at depth.

 

[rsingler]

Well, in that case, assuming the environmental seal stayed intact and deformed with depth, the relative IP provided by the unit probably dropped 5-12 psi for every 33fsw, because the environmental seal was preventing transmission of ambient pressure to the main diaphragm. That would make it a lot easier on the solenoid, lol. But I would expect the first stage to potentially provide inadequate O2 below 250 ft or even less, both via a solenoid or an orifice. I'm not too sure of CMF physics at low pressures, but it seems likely.

 

[Dsix36]

Well, in that case, assuming the environmental seal stayed intact and deformed with depth, the relative IP provided by the unit probably dropped 5-12 psi for every 33fsw, because the environmental seal was preventing transmission of ambient pressure to the main diaphragm. That would make it a lot easier on the solenoid, lol. But I would expect the first stage to potentially provide inadequate O2 below 250 ft or even less, both via a solenoid or an orifice. I'm not too sure of CMF physics at low pressures, but it seems likely.

I do recall someone that figured out there was a problem with deepish dives and that is why he resorted to just trimming some off the existing plunger instead. I think everything worked OK after that. At least he never mentioned any further problems to me.

OH yeah, the environmental seal did not have much longevity without a plunger and failed a couple of times.

 

[rjack321]

My investigations lead me to understand that the sealed Apeks (DS4 and alike) are apparently overbalanced and gain 0.2 IP per 10m of depth which will get to a point that will impact the O2 solenoid functioning properly.

Solenoids are tolerant of a huge range of IP. Unless you have plans for 200m dives you dont really need to worry about the overbalancing "feature"